A cheap, readily available steroid drug reduced deaths by a third in patients hospitalized with Covid-19 in a large study, the first time a therapy has been shown to possibly improve the odds of survival with the condition in the sickest patients.

Full data from the study have not been published or subjected to scientific scrutiny. But outside experts on Tuesday immediately embraced the top-line results. The drug, dexamethasone, is widely available and is used to treat conditions including rheumatoid arthritis, asthma, and some cancers.

In a statement, Patrick Vallance, the U.K. government’s chief scientific adviser, called the result “tremendous news” and “a ground-breaking development in our fight against the disease.” Scott Gottlieb, a former commissioner of the U.S. Food and Drug Administration, called it “a very positive finding” in an interview on CNBC. “I think it needs to be validated, but it certainly suggests that this could be beneficial in this setting.”